Many types of computer networks are known today, such as Local Area Networks (“LANs”), Wide Area Networks (“WANs”), intranets, and the Internet. For example, clients make requests via the Internet to servers which reside on LANs which are connected to the Internet. It is common for one or more Internet Service Providers (“ISPs”) to be logically interposed between the Internet and the LAN of a server, and for one or more edge routers to be physically and/or logically interposed between this LAN of the server and the ISP(s). Having more than one connection to the Internet is called “multihoming”. The use of two or more ISPs allows for load balancing and increased resiliency. The edge routers for the server periodically broadcast Border Gateway Protocol (“BGP”) announcements of the server network's Autonomous System Number (“ASN”) and associated routes leading to the server. BGP is defined in RFC 1771, and is an exterior gateway routing protocol used to share information between routers, or groups of routers, to determine efficient paths. The adjacent ISPs and routers receive these broadcasts. During normal operation, each ISP receives packets that include a source Internet Protocol (“IP”) address and a destination IP address, and then forwards or “routes” the packets to the destination IP address via the intervening router(s) to the server. (A packet is a piece of a message transmitted over a packet-switching network. One of the key features of a packet is that it contains the destination address in addition to the data. In IP networks, packets are often called datagrams.) The destination IP address may lead to a single server which can handle the request, a load balancer or proxy server for a pool of servers to handle the request or a gateway for the network on which the server or server pool resides. The servers at the destination IP address are sometimes called a “site” or “production site”. If the site furnishes web pages to the requester as an interface to the requested application, the destination server can also be called a “website”.
Often, there is a backup production site (“backup site”) on a backup network in case the original production site (“original site”) fails. There may be one or more ISPs for the backup site as well. When the original site fails, the edge routers of the original site stop their periodic BGP (Border Gateway Protocol) announcements of the original site Autonomous System Number (“ASN”) and associated routes. The ISPs of the original site notice the cessation of the ASN and its associated routes for the original site, and in response, update their routing table to remove any routes associated with this ASN. The ISPs of the original site propagate these changes throughout the Internet via BGP. At this time the original site's routes and IP addresses are unknown to the Internet. To re-route packets to the backup site, it was known to use Domain Name System (“DNS”) updates. (DNS is a system used to translate host and domain names to IP addresses.) These DNS updates change the IP address-hostname and IP address-domain name translations. Because this solution relies on hostnames and domain names, it does not support applications or implementations that require the original IP addresses to be maintained at the backup site. Additionally, DNS updates may take up to seventy two hours to propagate worldwide (depending on individual DNS Time To Live timout settings). Extra work is required to change IP addresses at the backup site and configure DNS properly (e.g. zone file modification). This extra work may translate to longer periods of outages. Another known solution is to install the same ISP at both sites. However, this may be costly depending on the ISP and the site(s). If the need arises to recover at an unplanned location it is likely that the same ISP may not be installed or available at this location in a timely fashion.
Accordingly, an object of the present invention is to expedite and facilitate re-routing of network packets to a backup site when an original site fails.